The present invention relates to a method and a device for widening tubular organs in general and to a method and a device for widening arteries in particular.
Devices and methods for widening tube shaped organs, in general and in the human body, in particular, are known in the art.
U.S. Pat. No. 5,716,410, to Wang et al, is directed to a catheter for vascular use. The catheter includes a directing mechanism and an inflatable balloon at the tip. The tip also includes a temporary stent, made of thermoplastic material. The catheter is inserted into the body of the patient, via a wide surface artery and the operator directs the catheter toward the destination location. When the tip is positioned at the destination location, then the operator pumps fluid to the balloon, via a tube, running along the catheter and starts inflating the balloon.
Reference is now made to FIG. 2, provided by Wang et al as FIG. 1, which is an illustration of a catheter, known in the art.
At the same time, the thermoplastic stent is heated, thereby unlocking its shape. The balloon, as it inflates, applies circumferencial pressure on the stent and the tubular organ, thereby forcing them to extend. Accordingly, the circumference of the tubular organ becomes larger. When the balloon brings the thermoplastic stent to the destination diameter, then the thermoplastic stent is cooled, thereby fixing its shape at a larger diameter, where it supports the tubular organ at an enlarged position.
Then, the operator, reduces the pressure within the balloon, which in turn deflates and becomes smaller than the enlarged circumference of the tubular organ. The thermoplastic stent is then kept within the tubular organ for a time period which may range from a few minutes to as long as a week. Finally, the thermoplastic stent is reheated, thereby unlocking its shape, and enabling its removal from the body of the patient.
It will be appreciated by those skilled in the art, that a balloon is often longer than the segment to be treated. Hence, the inflatable portion of the balloon extends beyond the desired segments to healthy segments, and can cause damage thereto.
Furthermore, when a balloon is inflated inside a blood vessel, it occludes the blood flow distally and becomes a full barrier for any blood flow therein. It will be appreciated by those skilled in the art that many blood vessel related balloon treatments are performed in coronary arteries. Accordingly, such a procedure, while blocking blood flow through the treated blood vessel, may cause ischemia or even cardiac arrest.
The balloon blocks the blood flow both in the axial (through the blood vessel) and radial directions blocking branches.
The complete obstruction, a balloon related treatment is usually limited to one or two minutes of inflation, since the patient can not tolerate long time inflations, because of severe pain and chest discomfort, due to ischemia.
It will be appreciated by those skilled in the art that a blood vessel is generally a flexible organ. This fact, combined with the short time period in which a balloon expands the circumference of the blood vessel, (as much as 40% of the cases) causes the balloon treated blood vessel to assume its original size (recoil) immediately, or within few months shortly after the treatment.
A stent is generally an element which is inserted into the tubular organ with the aid of a catheter. The initial shape of a stent is of an elongated cylinder, having a diameter which is smaller than the narrowed section of the tubular organ, through which it has to pass. At the beginning of the treatment, the stent is positioned in the stenosed segment.
Then, the circumference of the stent is widened, by various methods, known in the art. One of these methods includes inserting a balloon into the stent and applying pressure by inflating it therewith. Accordingly, the stent widens, thereby applying pressure on the narrowed blood vessel. As a result, the stent widens the cross section of the diseased segment.
Finally, the balloon is deflated and is removed from the stent, which remains in its widened position, forcing the widened blood vessel to remain at its new state. Afterwards, the stent is covered by local tissue and is anchored thereto. This poses a disadvantage in the usage of a stent since such a stent can not be removed. A stent is an alien element within a living organism, which might produce thrombus in it.
In many cases (15%-40%) instant stenosis occurs. The mechanism of this narrowing is intimal proliferation thereby causing a new blockage at the same location. It is known by those skilled in the art that sometimes, such a reoccurring blockage is difficult to treat and in some cases, surgery is needed, to remove and replace the clogged section.
In some instances the stent may be lost and migrate distally in the coronary artery, or sometimes in the aorta and its branches. The stent also can be stucked.
Shape memory effect (SME) is a phenomena, in shape memory alloys (SMA) of a reversible transition from one solid phase into the other (i.e., from Martensite into Austenite or from Austenite to Martensite). Heating the alloy causes the transition from Martensite into Austenite. Cooling the alloy causes the reverse transition, from Austenite into Martensite. NiTi alloys are examples for such shape memory alloys.
Martensite and Austenite are two solid state phases, which are typical for alloys. Each of these phases is characterized in a certain crystaline structure.
Basically there are two types of shape memory effects. The first type is called the one way shape memory effect (OWSM), where the material transits from one of the above phase states to the other, only once. The second type is called the two way shape memory effect (TWSM), where the material transits from one of the phase states to the other and back in a reversible process.
Shape memory alloys, such as Nixe2x80x94Ti, Nixe2x80x94Tixe2x80x94X, Cuxe2x80x94Nixe2x80x94Al, Cuxe2x80x94Znxe2x80x94Al, Fexe2x80x94Mnxe2x80x94Si, Nixe2x80x94Tixe2x80x94Co, Nixe2x80x94Cuxe2x80x94X, Nixe2x80x94Al and the like, are known in the art. These alloys exhibit a shape memory effect. In the martensite condition, the shape alloy material is relatively flexible and soft, and can be easily deformed. When the material undergoes the transition into an austenite state, it becomes more rigid, and is able to apply force and generate work, deform and enlarge the cross section of the blood vessel.
U.S. Pat. No. 5,540,713 to Shnepp-Pesch et al, is directed to an apparatus for widening a stenosis in a body cavity, also known as a shape memory stent. Shnepp-Pesch describes a stent made from a shape memory alloy, assuming a first predetermined shape at a first predetermined temperature and second predetermined shape at a second predetermined temperature. When heated from the first temperature to the second one, the shape memory stent changes its shape from a narrow generally cylindrical shape to a wider generally cylindrical shape.
Shnepp-Pesch describe a plurality of shapes which are applicable as shape memory stents. Reference is now made to FIGS. 1A-1H, provided by Shnepp-Pesch et al, as FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A and 4B, respectively. These figures describe four shape memory stent structures, each at two states, one narrowed and the other enlarged.
It will be appreciated by those skilled in the art that this stent basically suffers the same disadvantages as any other stent, known in the art, as listed above.
It is an object of the present invention to provide a system for opening and temporarily supporting generally tubular organs, in general and arteries in particular.
It is a further object of the present invention to provide a novel method for temporarily supporting a tubular organ, in general and vascular organs in particular.
In accordance with the present invention, there is thus provided a system for opening and temporarily supporting a section of a generally tubular organ. The system includes a dilation catheter which has an integrally connected shape memory catheter tip. The shape memory catheter tip is made of a shape memory alloy. The shape memory catheter tip assumes a first shape at a first temperature and a second shape at a second temperature. Accordingly, the shape memory catheter tip is inserted into the body of the patient, while being in a narrow shape and expands within the body of the patient.
According to one aspect of the invention, the shape memory catheter tip is generally hollow, thereby enabling flow of bodily fluid therethrough. It is noted that the flow of fluid can be performed both in a radial direction as well as in an axial direction.
The system can further include an energy control unit, connected to the dilation catheter, for controlling the temperature of the shape memory catheter tip and an energy transfer unit. The energy transfer unit is connected between the shape memory catheter tip and the energy control unit. It is generally located within the dilating catheter and transfers energy between the energy control unit and the catheter tip. According to one aspect of the invention, the energy transfer unit is connected to the shape memory catheter tip, thereby transferring energy to and from. According to another aspect of the invention, the energy transfer unit is not integrally connected to the shape memory catheter tip, thereby transferring energy to and from the vicinity of the catheter tip.
The shape memory catheter tip can include a generally cylindrical coil.
According to a further aspect of the invention, the first shape is generally the shape of a cylindrical coil having a first diameter and the second shape is generally the shape of a cylindrical coil having a second diameter. Hence, when the shape memory catheter tip transforms from the first shape to the second shape, it widens the organ, which is attached thereto, for example, an artery.
According to one aspect of the invention, the generally cylindrical coil has a solid cross section. According to one aspect of the invention, the generally cylindrical coil has a hollow cross section and hence, enables the flow of fluid therethrough.
It is noted that the generally cylindrical coil can have a cross section, which is selected from the list consisting of radial cross section, elliptical cross section, semi radial cross section, semi elliptical cross section, a near rectangular cross section and the like.
The energy transfer means can include a conduit or a plurality of conduits and the temperature control unit can accordingly include means for providing temperature controlled fluid towards the shape memory unit via the energy transfer means.
According to one aspect of the invention, the one of the conduits, is opened in the vicinity of the shape memory catheter tip, thereby releasing temperature controlled fluid in the vicinity of the shape memory catheter tip.
According to a further aspect of the invention, the shape memory catheter tip includes a generally cylindrical coil, having a hollow cross section, through which temperature controlled fluid can flow.
According to one aspect of the invention, the cylindrical coil is connected to one of the conduits at a first end, and is open at a second end. Hence the conduit transfers temperature controlled fluid to the shape memory catheter tip, via the first end, and the shape memory catheter tip releases the temperature controlled fluid via the second end.
According to another aspect of the invention, the cylindrical coil is connected to a first one of the conduits at a first end thereof, and to a second one of the conduits, at the second end thereof. Hence the first conduit transfers temperature controlled fluid to the shape memory catheter tip, via the first end, and the second conduit receives temperature controlled fluid from the shape memory catheter tip, via the second end.
It is noted that the temperature control unit can include a power supply unit, which is electrically connected to the shape memory unit, thereby electrically heating the shape memory unit from the first temperature to the second temperature. Accordingly, the energy transfer means can include an electricity conducting unit, such as electrical wires, which are electrically connected to the shape memory unit.
The shape memory alloy, used to manufacture the shape memory catheter tip can be selected from the list consisting of: Nixe2x80x94Ti, Nixe2x80x94Tixe2x80x94X, Cuxe2x80x94Nixe2x80x94Al, Cuxe2x80x94Znxe2x80x94Al, Fexe2x80x94Mnxe2x80x94Si, Nixe2x80x94Tixe2x80x94Co, Nixe2x80x94Cuxe2x80x94X, Nixe2x80x94Al and the like.
It is noted that the shape memory catheter tip can be characterized to operate at a plurality of temperatures. Accordingly, the first temperature is equal or below the temperature of the environment, in which the shape memory catheter tip is placed.
Alternatively the first temperature can be in the range of 38 degrees Celsius and 65 degrees Celsius or in the range of 42 degrees Celsius and 50 degrees Celsius. Similarly, the second temperature can be in the range of 5 degrees Celsius and 35 degrees Celsius or in the range of 20 degrees Celsius and 32 degrees Celsius. It is noted in the manufacturing process, the first and second temperatures can be swapped (i.e., the first temperature is lower than the second temperature).
In accordance with a further aspect of the present invention, the system further includes elastic means, such as a spring, which are attached to the shape memory catheter tip having an initial shape. The initial shape is generally similar to the first shape of the shape memory catheter tip. The elastic means apply force on the shape memory catheter tip so as to deform the shape memory catheter tip to the initial shape of the elastic means.
According to one aspect, where the shape memory catheter tip is made of a hollow cross section tube, the elastic means can be inserted within the shape memory unit. According to another aspect of the invention, the elastic means are attached to the shape memory unit, on the outside.
It is noted that the front section of the shape memory catheter tip can be shaped as a guiding front end.
Alternatively, the system according to the invention can further include a guiding unit having a guiding tip, wherein the guiding unit is located within the dilation catheter and the guiding tip extends beyond the shape memory catheter tip. Accordingly, the guiding tip is operable to move relative to the shape memory catheter tip.
It is noted that the first diameter can be smaller than the second diameter. Alternatively, the first diameter can be larger than the second diameter.
The shape of the shape memory catheter tip in the martensite state can be narrow with respect to the shape of the shape memory catheter tip in the austenite state. Alternatively, the shape of the shape memory catheter tip in the martensite state can be wider with respect to the shape of the shape memory catheter tip in the austenite state. With reference to the above elastic means, the initial shape assumes a shape which is similar to the shape of the shape memory catheter tip in the martensite state, and hence can be narrow or wide, respectively.
It is noted that the conduits which are connected to the catheter tip can be concentric or side by side.